Burst plugs are used in some downhole tools to provide a removable plug in the tool. Some fluid conveyed down hole tools, for example, include fluid passage bores that must be plugged for fluid conveyance, but are intended to be opened after placement to permit fluid flow therethrough. For example, in a pump down cement float, such as for example one of those described in PCT/CA2003/001889, filed Dec. 8, 2003 or Canadian patent application 2,311,160, published Dec. 9, 2001 (both to the present assignee), the float includes a bore along its length for passage downwardly therethrough of cement fluids, a check valve in the bore and a pressure responsive plug such as an expellable plug, also called a burst plug or disc, for holding pressure during pump down but removable, as by expelling or bursting at pressures above pumping pressure, to allow fluid flow through the bore, as controlled by the valve.
In those kinds of pump down cement floats, the float is conveyed down hole with the burst plug plugging the bore, but when desired, the fluid pressure above the float is increased to remove the plug from its plugging position in the bore. When pressuring up to burst the plug and open the bore, the check valve and/or the formation can be damaged by the surge of liquid that passes the check valve when the plug is removed.